1. Field of the Invention
This invention relates to a vehicle-tire-air-pressure sensing-and-indicating device. More specifically, the invention relates to means to notify the driver of low tire pressure. The invention pertains to the general type of arrangement in which pneumatic means connected to a vehicle tire drive a magnet inward or outward of the vehicle wheel to affect magnetic-field-responsive switch means mounted on the vehicle body adjacent the wheel, the switch means controlling indicating means within the vehicle.
2. Description of the Prior Art
In the prior art, there are a number of showings of vehicle-tire-pressure-warning systems employing magnets movably disposed on the wheel, the magnets being moved in correspondence to the pressure in the tire. An example is the U.S. Pat. No. 3,654,601 to Munson et al, granted Apr. 4, 1972. Another example is the U.S. Pat. No. 3,521,232 to Poole, issued July 21, 1970. The U.S. Pat. No. 2,629,086 to Ainsworth et al, issued Feb. 17, 1953, is similarly concerned with such an arrangement.
While the devices in the prior art are effective to some extent, they all require substantial modification to the wheel of the vehicle. Poole, mentioned above, for instance, requires a substantial opening in the rim of the wheel. The other devices mentioned involve one or a plurality of perforations in the body of the wheel to permit the passage of pneumatic tubes. Additionally, the prior devices have been difficult and awkward to connect to the magnet-moving means from the tire.